The present invention relates generally to facility management and control systems and, more particularly, to facility management and control systems and methods for use in the semiconductor wafer manufacturing industry to collect process data including particle measurement data from remote locations.
In order to monitor and control modern industrial processes, facility management and control systems have been developed. Facility management and control systems collect various types of process data. A facility management and control system can then analyze the process data for quality control purposes as described below.
The measurement instruments that provide the process data are typically distributed throughout the facility with the particular arrangement dependent upon the nature of the process being monitored and the configuration of the facility. In addition, various types of measurement instruments can be employed depending upon the process data that is to be collected. For example, measurement instruments are typically employed to measure process data such as temperatures, pressures, humidity levels, switch positions and the like. While these measurement instruments can operate independently, the process data provided by the measurement instruments that monitor a particular stage of a process are oftentimes collected by a programmable logic controller.
Although the measurement instruments are typically distributed at various locations throughout the facility depending upon the particular stage of the process that is to be monitored, facility management and control systems generally include a computer for collecting and processing the data provided by the various measurement instruments. The computer is typically located at a relatively centralized position, such as within a control room or the like. As such, the computer is generally remote from most, if not all, of the measurement instruments by being positioned in a different room of the same building or in another building altogether. By collecting the data provided by the measurement instruments or, more commonly, by one or more programmable logic controllers with a computer, the data can be more thoroughly analyzed such as by cross-checking or correlating the data obtained by measurement instruments that are designed to monitor different stages of the process.
The computer can process the data in various manners for quality control and other purposes. In this regard, the data can be examined from a historical perspective in an attempt to determine, after the fact, the processing conditions that existed during the fabrication of products that were eventually determined to be of either unusually high quality or unacceptably low quality. In order to avoid fabricating a number of unacceptable products prior to detecting the problem and taking corrective action to bring the process back into tolerance, the computer can compare the current process data to predetermined acceptable ranges of process data. As such, if the process data collected by the measurement instruments falls outside the predetermined range of acceptable process data, the central computer can trigger an alarm such that the process parameters can be quickly adjusted prior to fabricating a large number of unacceptable products.
One example of a process for which a facility management and control system has been developed is the wafer fabrication process. In this process, wafers, such as silicon wafers, undergo a number of different process steps in order to fabricate wafers having the desired characteristics, such as the desired resistivity, surface roughness, etc. A facilities management and control system that includes a computer and a number of distributed measurement instruments is particularly useful for a wafer fabrication process since slight variations in the process parameters can substantially alter the characteristics of the resulting wafers, thereby causing wafers that will be unacceptable to be fabricated as a result of only minor changes in the process parameters. A facilities management and control system is also advantageous for a wafer fabrication process since the throughput of a wafer fabrication process is relatively high such that it is desirable to detect variations in the process parameters as soon as possible in order to reduce the number of unacceptable wafers that are fabricated.
In a wafer fabrication process, one of the most important process parameters is the particle count at different stages. In this regard, wafers are subjected to various environments during the fabrication process, some of which are designed to be ultra-pure environments having relatively few particles or contaminants. For example, at different stages of the fabrication process, a wafer is typically washed with ultra-pure water, exposed to ultra-pure chemicals, subjected to high pressure gas, such as hydrogen or nitrogen, having relatively few particles or subjected to an aerosol having relatively few particles, such as within a cleanroom. During any of these stages of the fabrication process, it is desirable to measure the particles in the particular medium, such as the water, chemical, gas or aerosol.
Two types of particle measurements are accumulated particle counts and differential particle counts. Accumulated particle counts are a running total of the particles, typically having at least a predefined minimum size or diameter, detected within a window of time. Thus, an accumulated particle count is typically the sum of several measurements taken during the window of time. Conversely, differential particle counts measure the change in particles, also typically having at least a predefined minimum size, from one measurement to the next.
These particle measurements can then be used to monitor particle levels and to track changes in the particle levels. Historical trends can be identified and used to analyze particle data correlation with wafer quality and other manufacturing processes. Based upon historical trends and related process data, acceptable operating levels and/or thresholds for accumulated particle counts and differential particle counts can be established to maintain wafer fabrication quality standards. Since the accumulated and differential particle counts each provide somewhat different and useful data, it is therefore desirable to measure and track the accumulated particle counts and differential change in particle counts from measurement to measurement. As such, various particle measurement instruments have been developed and are commercially available to provide these particle counts.
Unfortunately, these conventional particle measurement instruments are generally unable to transmit the data, such as the particle counts, that has been collected to a computer that is remote from the particle measurement instruments in the same manner as other measurement instruments or programmable logic controllers. As such, dedicated computers were oftentimes co-located with the particle measurement instruments in order to collect and characterize the data. In order to correlate the data collected by the particle measurement instruments with the data collected by various other measurement instruments distributed throughout the wafer fabrication facility, technicians would have to manually collect the particle data from the dedicated computers associated with the respective particle measurement instruments distributed throughout the facility, such as by obtaining a printout of the particle data from each dedicated computer or downloading the particle data onto a computer diskette or the like. Typically, the particle data is then manually re-entered into a spreadsheet. By copying other process data from the facilities management and control system, i.e., the process data collected by other measurement instruments, and by exporting this other process data in spreadsheet format, this other process data can be merged with the particle data and the combined data set can be evaluated. As such, the various different types of data collected for the respective stages of the fabrication process can be correlated for training, quality control or other purposes.
As will be apparent, the manual collection and re-entry of the particle data can quickly become time consuming and is subject to errors during the manual re-entry process. As such, attempts have been made to connect the particle measurement instruments to a central computer by utilizing line drivers to transmit the particle data that is provided serially by the particle measurement instruments distributed about the facility to the central computer. Unfortunately, the line drivers are notoriously prone to the introduction of errors, particularly at the relatively high bit rates that would be utilized during the transmission of the particle data.
A facility monitoring system has been developed by Particle Measuring Systems, Inc. (PMS) of Boulder, Colo. that permits the particle data collected by PMS particle measurement instruments to be transmitted to a central computer via a computer network by using TCP/IP protocol. In addition to transmitting the particle data, the PMS particle measurement instruments generally include ports to which other measurement instruments can be connected. The PMS particle measurement instruments can therefore transmit the process data collected by these other measurement instruments along with the particle data to the central computer. For example, measurement instruments that can be connected to a PMS particle measurement instrument include a temperature sensor, a pressure gauge and the like.
Unfortunately, the PMS facility monitoring system does not interface with the measurement instruments of other vendors and therefore does not permit the process data collected by the measurement instruments of other vendors to be transmitted via the computer network for collection by the computer. In addition, the central computer of a PMS facility monitoring system does not interface with measurement instruments designed to measure process data other than particle data unless these other measurement instruments are first connected to a PMS particle measurement instrument, and the process data collected by these other measuring instruments is transmitted along with the particle data by the PMS particle measurement instrument. Thus, the PMS facility monitoring system does not permit measurement instruments that are independent of the PMS particle measurement instruments to separately transmit process data, such as temperatures, pressures, humidity levels, switch positions or the like, via the computer network for processing and correlation with the particle data provided by the PMS particle measurement instruments. As such, it would be desirable to provide a facilities management and control system and method that include a computer network that could communicate in a reliable manner with a variety of measurement instruments, including particle measurement instruments, without requiring manual intervention in order to collect and re-enter the particle data and without requiring all process data to be routed through the particle measurement instruments.
A system and method are provided for collecting, storing, and displaying particle measurement data from a plurality particle measuring instruments and other process data from process data collection devices. With respect to the particle measurement data, the system and method collect, store and display accumulated particle counts from multiple particle measuring instruments. As such, both the process data and the particle measurement data including the accumulated particle counts are provided to a computer network. A converter is therefore provided to convert the particle measurement data including the accumulated particle counts and the other process data to comply with the computer network protocol such that the data is in a readable form. The computer network transmits the particle measurement data including the accumulated particle counts the other process data and stores the data accordingly. The particle measurement data including the accumulated particle counts and the other process data may then be displayed through a graphic user interface.
Additional aspects of the system and method provide for the collecting, storing, and displaying of other particle measurement data. For example, it is advantageous to obtain differential particle counts from the particle measuring instruments. Differential particle counts can be treated in a similar manner as the accumulated particle counts, which include converting the differential particle counts in accordance with a network protocol, transmitting the differential partial counts via the computer network, storing the differential particle counts, and allowing a user to retrieve and display the differential particle counts through the graphic user interface. Other valuable data that is collected, stored and displayed may include instrument data associated with the particle measuring instruments themselves. This data may include a unique device label identifying the respective particle measuring instrument. It may also include date, time, manifold position, and power supply voltage levels associated with each particle measuring instrument and, in turn, with each particle count.
The computer network may include a memory buffer to collect the particle measurement data and the processed data. In this regard, once the data is received via the computer network, a parsing function can parse the data according to its type, such as by separating the different particle counts, instrument data and the process data. The different types of particle counts may then be separately stored in the memory buffer for later retrieval. These instrument data associated with the particle counts may then be used to identify or name the individual particle counts as they are stored.
Another advantageous aspect of the present invention provides for collecting, storing, and displaying accumulated and differential particle counts according to their particle size. In this embodiment, the particle measuring instrument distinguishes the particle measurements according to a predetermined particle size. These particle counts are then collected, stored, and displayed in the same manner as previously discussed. The graphic user interface allows selection of this predetermined particle size, however, such that quality control parameters of the process may be assessed and/or such that the same quality control parameters may be reviewed in a different level of detail.
There are a multitude of possible instruments from which the foregoing system and method may retrieve data. For example, particle measuring instruments that measure particle counts in aerosol mediums, gas mediums, and liquid mediums may be utilized. Additionally, the process data collecting device may collect from devices including a temperature monitoring device, a relative humidity monitoring device, and pressure monitoring device.
The present invention also includes an advantageous method for collecting, storing, and displaying particle measurement data and other process data. With respect to the particle measurement data, accumulated particle counts from particle measuring instruments in remote locations may be collected, stored and displayed. Process data, other than particle counts, is also determined at remote locations by devices that are independent of the particle measuring instruments. The process data may include relative humidity, temperature, and pressure. This process data and particle measurement data including accumulated particle count data may then be transmitted via a computer network for storage and display. In one aspect, the particle measurement data may also include differential particle counts. Both types of particle counts may be discriminated according to particle size.
Therefore, the system and method of the present invention collects a wide variety of data, including both particle measurement data and other process data, in an integrated manner. With respect to the particle measurement data, the system and method collect and analyze accumulated particle counts and, in some embodiments, differential particle counts in order to provide additional information for facility management purposes or the like. As such, the system and method of the present invention provide a tool to enable greater control and more detailed monitoring of a facility, such as a cleanroom.